“We haven’t been able to answer the question, ‘Does life exist beyond Earth?’ But following the water is a critical element of that. We now have, I think, great opportunities in the right locations on Mars to thoroughly investigate that.” – James L. Green

NASA is also thinking about sending a spacecraft in the 2020 to one of these regions to directly look for life.

The water we are talking about is in form of hydrated salts, but as per Alferd S. McEwen, a professor of planetary geology at the University of Arizona “There pretty much has to have been liquid water recently present to produce the hydrated salt.”

By “recently,” Dr. McEwen said he meant “days, something of that order.”

We knew that the large amounts of water is present in form of frozen solid in the polar ice caps. Also there have been hints of liquid water, but none have proved convincing.

In 2011, the photographs from the orbiter shows dark streaks descending along slopes of mountains. The streaks lengthened during summer, faded in winters, then reappeared the next year.

Scientists suspected that water played a critical role in this behaviour, similar to the way concrete darkens when wet and returns to its original color when dry. But that was just a guess.

But now, the signs of the salt disappeared when the streaks faded is very definitive that there is some sort of liquid water.

So how does the water remains liquid on Mars?

The salts lower the freezing temperature, and the water remains liquid. The average temperature of Mars is about -70 degrees Fahrenheit, but in summers the temperature at Equator can reach an almost 70 degrees.

The scientists are still not sure about where the liquid water might be coming from on Mars. The current readings of the planet’s atmosphere point to very low humidity near the surface, but there’s also a chance that it might be coming from underground aquifers on the planet, which seep out when things warm up.

What about presence of Life?

Christopher P. McKay, an astrobiologist at NASA’s Ames Research Center in Mountain View, Calif., does not think the recurring slope lineae are a promising place to look. For the water to be liquid, it must be so salty that nothing could live there, he said. “The short answer for habitability is it means nothing,” he said.

He pointed to Don Juan Pond in Antarctica, which remains liquid year round in subzero temperatures because of high concentrations of calcium chloride salt. “You fly over it, and it looks like a beautiful swimming pool,” Dr. McKay said. “But the water has got nothing.”

We’ve known for a while now that Mars currently holds large reserves of frozen water at its poles, and that it had large oceans billions of years ago. But this discovery will have a huge impact on Martian missions in near future.